Condensation reaction



Patented May 9. 1939 UNITED STATES PATENT OFFICE 2,158,031 commnsa'rron nnAc'rroN Donald J. Loder, Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmlngton, Del., a corporation of Delaware No Drawing. Application October 26, 1935, Serial No. 46,875

4 Claims.

This invention relates to a new catalyst for organic synthesis and more particularly to boron halide catalysts.

In the Friedel-Crafts reactions for the synthesis 6 of aromatic hydrocarbons, ketones and triphenyl and water. The aluminum halide and analogous halides are thus hydrated and the involved expensive steps required to reconvert them to the 20 anhydrous form generally renders syntheses of this nature commercially unattractive.

An object of the present invention is to provide a new class of condensing or catalytic agents prepared from boron-halogen containing com- 26 pounds. A further object of the invention is to provide a new and improved class of condensing agents particularly for reactions requiring an acid type condensing agent, such, for example, as: the interaction of alcohols with carbon monoxide to obtain acids and esters, the interaction of olefines and carbon monoxide to produce acids and esters, the interaction of organic acids with olefines to provide high molecular weight esters, and many of the reactions of the Friedel-Crafts 35 type. A still further object of the invention is to provide hydrated boron halide catalysts for accelerating organic reactions of the above types. Other objects and advantages of the invention will hereinafter appear.

I have found that organic reactions such as the preparation of organic acids and their esters by the interaction of carbon monoxide with alcohols, ethers, esters, olefines and reactants which decompose to form such compounds, as well as the Friedel-Crafts type of reactions in which water is not detrimental, can be catalyzed with certain hydrated boron trihalides. These catalysts are particularly effective in reactions requiring superatmospheric pressures. They are also well fitted for catalyzing generally such organic condensation reactions in which water is not detrimental and which require an acidic type catalyst; they are especially adapted for reac- 56 tions in which carbon" monoxide is one of the reactants. A few of the r'eactions for which these catalysts are suitable include:

(i) Olefine+CO- acid and/or ester (2) ROH+CO- RCOOH and/0r HCOOR (3) Rz0+CO+HOH- RCOOH and/or HCOOR and/or RCOOR (4) RH+CO- RCOH (5) 2H2CO+CH3.CH:CH2-

CHrCH-CHg-CH,

R1-CH-CH-Ri R: H. Y

(7) CO+HOH- HCOOH (8) RCOOH-l-olefine-mster (9) Benzene+olefinealkyl benzene (10) Pheno1+olefine phenol ether and/or substituted phenol (11) Phenol+RCOOH- phenyl alkyl ketone In the above reactions R may indicate an alkyl, aryl or aralkyl grouping. In Example (1) by utilizing ethylene as the olefine, acetic acid and/ or ethyl acetate would be formed, and in Reaction (2) by substituting the alkyl group, CH3 for R, methanol would be reacted with carbon monoxide to give acetic acid and/or methyl formate. In Reaction (4) by substituting the aryl, CeHs, for R, benzene would react with CO to form benzaldehyde.

My preferred condensing agents for reactions such as those illustrated above and their equivalents are the boron trihalides associated with water in the ratio ranging preferably from one to five mols per mo of boron trihalide. More specifically they include the boron trihalides associated with water as a mono-, di-, triand quatri-hydrate of the trichloride, trifiuorlde, tribromide, or triiodide of boron. Furthermore, as the boron trihalides form intermediate products which may be designated as intermediate hydrates between those definitely stated above, it is understood that such hydrates are likewise suitable as condensing agents.

It has been stated heretofore that the principal difiicultyencountered in the use of anhydrous halides, and more particularly aluminum halide, arose from the necessary destruction of the condensing agent prior to the recovery of the products oi the reaction. An additional difllculty in the use of such agents is encountered in handling the anhydrous agents and maintaining them in the anhydrous form. The condensing agents of the present invention can be readily separated by distillation, extraction, decantation or by other means from the reaction products and the recovered agents, generally without the necessity of purification, can be reused directly to accelerate another reaction. The striking advantages of these recoverable highly reactive condensing agents over the anhydrous condensing agents are self-evident.

Generally the condensing agents may be prepared by reacting a liquid halogen acid with a boric acid. For example, three mols of liquid hydrofluoric acid may be reacted with one mol of solid orthoboric acid to give the liquid trihydrate of boron trifluoride or three mols of liquid hydrofluoric-acid may be reacted with one-half a mol of metaboric acid to give the dihydrate of boron trifluoride.

I shall now describe more specifically methods of preparing the condensing agent of the inventionand also processes in which they may be used but it will be understood that the details therein given will not limit the scope of the invention.

Example 1.1696 parts by weight of solid orthoboric acid are placed in a suitable pressure sustaining receptacle and 1643 parts by weight of liquid hydrofluoric acid are added thereto. The temperature of the exothermic reaction is kept at approximately 10 C., and when the reaction of the hydrofluoric acid with the boric acid is complete a liquid, fairly mobile trihydrate of boron trifiuoride, having a specific quantity 01 1.500 at,

20 0., is obtained.

Example 2.-468 parts by weight of liquid hy drofluoric acid are combined as in Example 1 with 1'75 parts by weight of metaboric acid. The liquid catalyst obtained is apparently a dihydrate of boron trifiuoride having a specific gravity of 1.625 at 20" C.

As has already been emphasized the condensing agents of the present invention may be utilized in a number of reactions and are most advantageously employed in. condensation reactions in which water is not detrimental. I shall now give several examples illustrating types of processes in which my preferred condensing agents are employed, but the utility of the catalysts is not limited by or to these processes.

Example 3.205 parts by weight of the trihydrate of boron trifiuoride obtained as described in Example 1 are placed in a pressure resisting autoclave and 54 parts by weight of methanol added. The autoclave is closed and carbon monoxide is added to the mixture contained therein until a pressure of approximately 900 atmospheres is attained. The temperature is held at approxi mately 260 C., and the reaction is continued until analysis shows that an equivalent weight of carbon monoxide has reacted with the methanol present. The pressure is released and the acetic acid distilled from the reaction mixture, steam being added during the distillation to maintain a fairly constant water to boron trifluoride ratio. A 79% yield of acetic acid was obtained when this reaction was conducted under the above conditions.

Example 4.A mixture of 64 parts by weight oi methanol and 1'75 parts by weight of the catalyst prepared in accord with the directions given in Example 2 was charged into a pressure shaker tube. The mixture was heated to 240-250 0.,

under a CO pressure of approximately900 atmospheres for about 1%, hours during which a pressure drop of approximately 5'70 atmospheres oc-,

curred. The tube was cooled, the pressure discharged, and the product again heated to 160 C., under cylinder ethylene pressure for approximately of an hour during the course of which treatment a considerable pressure drop occurred. After cooling, the product was discharged and distilled directly giving a volume of crude ethyl acetate of 58.8 parts by weight having a boiling range of 61-'l2 C. The distillation wascontinued and acetic acid and-an acetic acid-boron fluoride addition compound condensed in the distillate.

Example 5.Ethanol was reacted according to the conditions and procedure given in Example 1 with a yield of 45-50% of the amount of propionic acid which is theoretically obtainable according to the equation:

Example 6.Formalin, 1'72 parts by weight, was caused to absorb 150 parts of boron fluoride gas. The resulting mixture absorbed propylene at from 0 C.-20 C., and one atmosphere pressure, forming a product which, when made alkaline, and distilled, yielded a series of formals. The lower boiling products (distilling at 30 to 123 C.,) were separated by salting out; the material distilling over below C., was purified by redistillation and the boiling point of the chief constituent, butylene glycol cyclic formal, was 113-1143 0. The higher boiling formals were obtained by continuing the distillation and collecting fractions between 123 and 250 C. Still higher boiling compounds remained in the residue. The yield of the low boiling products, obtained in the salting out process was .56 parts by weight and the yield of products boiling at 123 C. to 250 C., was 15- parts by weight.

My condensing agents may be used in various proportions which are governed by the type of reaction. I In the absence of addition agents such as metal oxides or powdered metals, for example, nickel and nickel oxides, they may be used in proportions ranging from 0.25 to 2.0 mols or higher calculated on the boron halide present per mol of the major reactant while in the presence of'addition agents much lower amounts may be employed, say, generally, from 1 to 5% and, in some instances, higher percentages may be required. The activity of the addition agent determines in large measure the amount required, the particular reaction as well as the temperature and pressure conditions employed also being considered.

As indicated in the examplesthereactions herein involve the addition of one compound to another to form a third compound. Accordingly it will be understood that when the words "condense, condensing,andcondensationare used herein, they designate such reactions whichare well illustrated by the equations given on page 1.

From a consideration of the above specification it will be realized that many changes may be made in the catalysts herein described and the method of their preparation without departing from the invention or sacrificing any of the advantages that may be derived therefrom.

I claim:

1. In a liquid phase process involving an organic condensation reaction of carbon monoxide with a member of the group consisting of olefines, alcohols, and ethers, the steps which comprise effecting the reaction in the presence of boron triiluoride associated with from 1 to 5 mols condensation reaction of carbon monoxide with a member of the group consisting of oleflnes. alcohols, and ethers, the steps which comprise efiecting the reaction in the presence of a trihydrate of boron trifluoride and recovering from the products of the reaction boron trifluoride associated with water.

4. The process of claim 1 wherein the boron fluoride associated with water is recovered from the reaction product by distillation and reused 10 for the same organic condensation reaction.

DONALD J. LODER. 

